1. Field of the Invention
The present invention is directed to System-on-a-Chip (SoC) devices, and more particularly to a method and system for enabling software running on a SoC device to request a change in power state directly, without having to adjust external board level states.
2. Description of the Related Art
The term “system-on-a-chip’ or SoC commonly refers to an integrated circuit on which all of the necessary electronic circuits and parts are packaged to create a complete “system” (e.g. a hand-held or vehicle-mounted computer, cell phone, digital camera, etc.). Such circuits normally include a system controller (e.g. a microcontroller or microprocessor), memory, timing sources (e.g. clocks), peripherals and external interfaces to analog and/or digital devices. These components are interconnected by a plurality of busses, such as the High-performance Bus (AHB) and Advanced Peripheral Bus (APB) defined in the Advanced Microcontroller Bus Architecture (AMBA), developed by ARM Ltd.
SoC devices typically include a Power Management Unit (PMU) that controls power functions, such as monitoring power connections and battery charges, controlling power to SoC components, and controlling device booting (e.g. cold start and reset). The PMU is conventionally isolated from software control and responds only to external events, such as hardware resets, voltage monitoring, watchdog events, etc. Consequently, it is not possible for the PMU to control changes in power state (e.g. re-boot the SoC) without an external hardware trigger event that meets predetermined threshold conditions.